Perhaps the most important part of the post:

SHIELD Experience Upgrade 5.2 is required for USB tuner support and the ability to save recorded shows to a NAS. Upgrade 5.2 will be released on a rolling basis in early June starting with SHIELD Preview Program members.

Is Plex pretty much a waste on Mi Box considering it doesn't support USB tuners? I would really like an OTA system/interface like Plex but don't want to move off Mi Box. Any solutions?

Reading this article it says they used the WinTV-DualHD USB tuner.

Is this officially supported now?